1979
During the 1979 Tour de France, the leader of the mountains classification Giovanni Battaglin tested positive for doping in stage 13. He was penalized by 10 minutes in the general classification, lost the points that he earned in stage 13 and received 10 penalty points in the mountains classification. Battaglin was still able to win the mountains classification.
Frans Van Looy and Gilbert Chaumaz also tested positive for doping during the Tour. After the Tour de France had finished, Joop Zoetemelk was found to have used doping, which he confessed later. Zoetemelk was penalized by 10 minutes in the general classification, but kept his second place.
Read more about this topic: List Of Doping Cases In Cycling, 1970s